Most battery charging devices provided with electronics devices, such as mobile phones and laptop computers, provide a fixed voltage source to recharge batteries. The required voltage and current profile for charging the battery is, in general, provided by electronic circuits, either within the charging device itself or within the battery. This allows flexibility in the choice of chargers and also serves to protect the device from potential damage from the use of inappropriate chargers.
Recently, there has been a move toward the use of wireless battery charging devices. Most wireless mobile charging solutions rely on inductive coupling. With inductive coupling, the charging station takes the form of a mat or other flat surface. Inside the mat are one or more inductive coupling coils. The mat itself is connected to an external source of power that is used to recharge the battery. Since the electricity coming to most homes is alternating current, the mat provides the electricity the coils need to generate a changing magnetic field. In some instances, a special case or attachment is connected to the electronics device to take advantage of this magnetic field and has a matching coil for the inductor coils. The electronics device is placed on the charging surface such that the coils overlap. The inductor coils inside the mat generates the magnetic field, which induces a flow of electricity inside the matching coil. This electricity then recharges the battery of the electronics device.
Another approach used by wireless battery charging devices utilizes conductive charging mats to transfer power when charging a battery. Conductive charging mats create a direct electric circuit between a mobile device and a charging surface. Typically, the surface of the charging device has strips of electrically conductive material embedded in it such that when a electronics device with corresponding electrical contacts touches these strips of metal, electricity flows into the battery of the electronics device.